Process for polymerizing 1-butene

ABSTRACT

A process for polymerizing 1-butene, optionally with up to 30% by mol of ethylene, propylene or an alpha olefin of formula CH 2 ═CHT wherein T is a C 3 -C 10  alkyl group, in the presence of a catalyst system obtainable by contacting a metallocene compound of formula (I) Wherein M is an atom of a transition metal; X, is a hydrogen atom, a halogen atoms or a hydrocarbon group; R 1 , R 2 , R 5 , R 6 , R 7 , R 8  and R 9  are hydrogen atoms or hydrocarbon groups; with the proviso that at least one of R 6  or R 7  is a C 1 -C 20  alkyl group; R 3  and R 4  are C 1 -C 20  alkyl groups; and an alumoxane and/or a compound capable of forming an alkyl metallocene cation.

The present invention relates to a process for polymerizing 1-butene byusing metallocene compounds and to the isotactic 1-butene polymersobtained thereby.

Isotactic 1-butene polymers are well known in the art. In view of theirgood properties in terms of pressure resistance, creep resistance, andimpact strength they have a lot of uses such as the manufacture of pipesto be used in the metal pipe replacement, easy-open packaging and films.

1-Butene (co)polymers are generally prepared by (co)polymerzing 1-butenein the presence of TiCl₃ based catalysts components together withdiethylaluminum chloride (DEAC) as cocatalyst. In some cases diethylaluminum iodide (DEAI) is also used in mixtures with DEAC. The thusobtained polymers, however, generally do not show satisfactorymechanical properties. Furthermore, in view of the low yields obtainablewith the TiCl₃ based catalysts, the 1-butene polymers prepared withthese catalysts have a high content of catalyst residues (generally morethan 300 ppm of Ti) which lowers the properties of the polymers makingit necessary a deashing step.

1-Butene (co)polymers can also be obtained by polymerizing the monomersin the presence of a stereospecific catalyst comprising (A) a solidcomponent comprising a Ti compound and an electron-donor compoundsupported on MgCl₂; (B) an alkylaluminum compound and, optionally, (C)an external electron-donor compound. A process of this type isdisclosed, for instance, in EP-A-172961 and in WO99/45043. Recently,metallocene compounds have been proposed for producing 1-butenepolymers. In Macromolecules 1995, 28, 1739-1749,rac-dimethylsilylbis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichlorideand methylaluminoxane have been used for polymerizing 1-butene. Theyield of the process is not indicated and the molecular weight of theobtained polymer (Mn) is very low. In Macromol. Rapid Commun. 18,581-589 (1997), rac- andmeso-[dimethylsilylenebis(2,3,5-trimethyl-cyclopentadienyl)]zirconiumdichloride have been used for the polymerization of 1-butene. The yieldsof the process and the molecular weight of the obtained polymers arerather low.

In WO 02/16450, 1-butene polymers endowed with low isotacticity aredescribed. These polymers are obtained by using a specific class ofdouble-bridged metallocene compounds.

In the international application WO 03/042258, 1-butene polymersobtained with metallocene compounds wherein a π ligand is acyclopentadithiophene moiety are described. It has now been found that,by selecting a specific substitution pattern in the other n moiety ofthe metallocene compound, the molecular weight of the obtained polymerscan be further increased and, at the same time, obtained in high yields.

Thus, according to a first aspect, the present invention provides aprocess for preparing 1-butene polymers, said process comprisingpolymerizing 1-butene or copolymerizing 1-butene with ethylene,propylene or an alpha-olefin of formula CH₂═CHT wherein T is a C₃-C₁₀alkyl group, in the presence of a catalyst system obtainable bycontacting:

-   (A) a metallocene compound belonging to the following formula (I):

wherein:M is an atom of a transition metal selected from those belonging togroup 3, 4, or to the lanthanide or actinide groups in the PeriodicTable of the Elements; preferably M is zirconium titanium or hafnium;X, equal to or different from each other, is a hydrogen atom, a halogenatom, a R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ group wherein R is alinear or branched, saturated or unsaturated C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkylradical, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; and R′ is a C₁-C₂₀-alkylidene,C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylideneradical; preferably X is a hydrogen atom, a halogen atom, a OR′O or Rgroup; more preferably X is chlorine or a methyl radical;R¹, R², R⁵, R⁶, R⁷, R⁸ and R⁹, equal to or different from each other,are hydrogen atoms, or linear or branched, saturated or unsaturatedC₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl orC₇-C₂₀-arylalkyl radicals, optionally containing heteroatoms belongingto groups 13-17 of the Periodic Table of the Elements; or R⁵ and R⁶,and/or R⁸ and R⁹ can optionally form a saturated or unsaturated, 5 or 6membered rings, said ring can bear C₁-C₂₀ alkyl radicals assubstituents; with the proviso that at least one of R⁶ or R⁷ is a linearor branched, saturated or unsaturated C₁-C₂₀-alkyl radical, optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably a C₁-C₁₀-alkyl radical;preferably R¹, R², are the same and are C₁-C₁₀ alkyl radicals optionallycontaining one or more silicon atoms; more preferably R¹ and R² aremethyl radicals;R⁸ and R⁹, equal to or different from each other, are preferably C₁-C₁₀alkyl or C₆-C₂₀ aryl radicals; more preferably they are methyl radicals;R⁵ is preferably a hydrogen atom or a methyl radical;R⁶ is preferably a hydrogen atom or a methyl, ethyl or isopropylradical;R⁷ is preferably a linear or branched, saturated or unsaturatedC₁-C₂₀-allyl radical, optionally containing heteroatoms belonging togroups 13-17 of the Periodic Table of the Elements; preferably aC₁-C₁₀-alkyl radical; more preferably R⁷ is a methyl or ethyl radical;otherwise when R⁶ is different from a hydrogen atom, R⁷ is preferably ahydrogen atomR³ and R⁴, equal to or different from each other, are linear orbranched, saturated or unsaturated C₁-C₂₀-alkyl radicals, optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably R³ and R⁴ equal to or different from eachother are C₁-C₁₀-alkyl radicals; more preferably R³ is a methyl, orethyl radical; and R⁴ is a methyl, ethyl or isopropyl radical;

-   (B) an alumoxane or a compound capable of forming an alkyl    metallocene cation; and optionally-   (C) an organo aluminum compound.

Metallocene compounds of formula (I) have been described, for example,in WO 01/47939.

Preferably the compounds of formula (I) have formula (Ia) or (Ib):

Wherein

M, X, R¹, R², R⁸ and R⁹ have been described above;R³ and R⁴, equal to or different from each other, are linear orbranched, saturated or unsaturated C₁-C₂₀-alkyl radicals, optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably R³ and R⁴ equal to or different from eachother are C₁-C₁₀-alkyl radicals; more preferably R³ is a methyl, orethyl radical; and R⁴ is a methyl, ethyl or isopropyl radical; R⁶ and R⁷are linear or branched, saturated or unsaturated C₁-C₂₀-alkyl radicals,optionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements; preferably C₁-C₁₀-alkyl radicals; morepreferably R⁷ is a methyl or ethyl radical; and R⁶ is a methyl, ethyl orisopropyl radical.

Alumoxanes used as component B) can be obtained by reacting water withan organo-aluminium compound of formula H_(j)AlU_(3-j) orH_(j)Al₂U_(6-j), where U substituents, same or different, are hydrogenatoms, halogen atoms, C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl or or C7-C20-arylalkyl radical, optionally containingsilicon or germanium atoms with the proviso that at least one U isdifferent from halogen, and j ranges from 0 to 1, being also anon-integer number. In this reaction the molar ratio of Al/water ispreferably comprised between 1:1 and 100:1. The molar ratio betweenaluminium and the metal of the metallocene generally is comprisedbetween about 10:1 and about 20000:1, and more preferably between about100:1 and about 5000:1. The alumoxanes used in the catalyst according tothe invention are considered to be linear, branched or cyclic compoundscontaining at least one group of the type:

wherein the substituents U, same or different, are described above.

In particular, alumoxanes of the formula:

can be used in the case of linear compounds, wherein n¹ is 0 or aninteger from 1 to 40 and the substituents U are defined as above, oralumoxanes of the formula:

can be used in the case of cyclic compounds, wherein n² is an integerfrom 2 to 40 and the U substituents are defined as above. Examples ofalumoxanes suitable for use according to the present invention aremethylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO),tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO),tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) andtetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO). Particularly interestingcocatalysts are those described in WO 99/21899 and in WO01/21674 inwhich the alkyl and aryl groups have specific branched patterns.Non-limiting examples of aluminium compounds according to WO 99/21899and WO01/21674 are:

tris(2,3,3-trimethyl-butyl)aluminium, tris(2,3-dimethyl-hexyl)aluminium,tris(2,3-dimethyl-butyl)aluminium, tris(2,3-dimethyl-pentyl)aluminium,tris(2,3 dimethyl-heptyl)aluminium,tris(2-methyl-3-ethyl-pentyl)aluminium,tris(2-methyl-3-ethyl-hexyl)aluminium,tris(2-methyl-3-ethyl-heptyl)aluminium,tris(2-methyl-3-propyl-hexyl)aluminium,tris(2-ethyl-3-methyl-butyl)aluminium,tris(2-ethyl-3-methyl-pentyl)aluminium,tris(2,3-diethyl-pentyl)aluminium,tris(2-propyl-3-methyl-butyl)aluminium,tris(2-isopropyl-3-methyl-butyl)aluminium,tris(2-isobutyl-3-methyl-pentyl)aluminium,tris(2,3,3-trimethyl-pentyl)aluminium,tris(2,3,3-trimethyl-hexyl)aluminium,tris(2-ethyl-3,3-dimethyl-butyl)aluminium,tris(2-ethyl-3,3-dimethyl-pentyl)aluminium,tris(2-isopropyl-3,3-dimethyl-butyl)aluminium,tris(2-trimethylsilyl-propyl)aluminium,tris(2-methyl-3-phenyl-butyl)aluminium,tris(2-ethyl-3-phenyl-butyl)aluminium,tris(2,3-dimethyl-3-phenyl-butyl)aluminium,tris(2-phenyl-propyl)aluminium,tris[2-(4-fluoro-phenyl)-propyl]aluminium,tris[2-(4-chloro-phenyl)-propyl]aluminium,tris[2-(3-isopropyl-phenyl)-propyl]aluminium,tris(2-phenyl-butyl)aluminium, tris(3-methyl-2-phenyl-butyl)aluminium,tris(2-phenyl-pentyl)aluminium,tris[2-(pentafluorophenyl)-propyl]aluminium,tris[2,2-diphenyl-ethyl]aluminium andtris[2-phenyl-2-methyl-propyl]aluminium, as well as the correspondingcompounds wherein one of the hydrocarbyl groups is replaced with ahydrogen atom, and those wherein one or two of the hydrocarbyl groupsare replaced with an isobutyl group.

Amongst the above aluminium compounds, trimethylaluminium (TMA),triisobutylaluminum (TIBAL), tris(2,4,4-trimethyl-pentyl)aluminum(TIOA), tris(2,3-dimethylbutyl)aluminium TDMBA) andtris(2,3,3-trimethylbutyl)aluminum (TTMBA) are preferred.

Non-limiting examples of compounds able to form an alkylmetallocenecation are compounds of formula D⁺E⁻ wherein D⁺ is a Brønsted acid, ableto donate a proton and to react irreversibly with a substituent X of themetallocene of formula (I) and E⁻ is a compatible anion, which is ableto stabilize the active catalytic species originating from the reactionof the two compounds, and which is sufficiently labile to be able to beremoved by an olefinic monomer. Preferably, the anion E⁻ comprises ofone or more boron atoms. More preferably, the anion E⁻ is an anion ofthe formula BAr₄ ⁽⁻⁾, wherein the substituents Ar which can be identicalor different are aryl radicals such as phenyl, pentafluorophenyl orbis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate isparticularly preferred examples of these compounds are described in WO91/02012. Moreover, compounds of the formula BAr₃ can conveniently beused. Compounds of this type are described, for example, in thepublished International patent application WO 92/00333. Other examplesof compounds able to form an alkylmetallocene cation are compounds offormula BAr₃P wherein P is a substituted or unsubstituted pyrrolradicals. These compounds are described in WO01/62764. Other examples ofcocatalyst can be found in EP 775707 and DE 19917985. Compoundscontaining boron atoms can be conveniently supported according to thedescription of DE-A-19962814 and DE-A-19962910. All these compoundscontaining boron atoms can be used in a molar ratio between boron andthe metal of the metallocene comprised between about 1:1 and about 10:1;preferably 1:1 and 2.1; more preferably about 1:1.

Non limiting examples of compounds of formula D⁺E⁻ are:

-   Triethylammoniumtetra(phenyl)borate,-   Tributylanunoniumtetra(phenyl)borate,-   Trimethylammoniumtetra(tolyl)borate,-   Tributylammoniumtetra(tolyl)borate,-   Tributylammoniumtetra(pentafluorophenyl)borate,-   Tributylammoniumtetra(pentafluorophenyl)aluminate,-   Tripropylammoniumtetra(dimethylphenyl)borate,-   Tributylammoniumtetra(trifluoromethylphenyl)borate,-   Tributylammoniumtetra(4-fluorophenyl)borate,-   N,N-Dimethylaniliniumtetra(phenyl)borate,-   N,N-Diethylaniliniumtetra(phenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)boratee,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)aluminate,-   Di(propyl)ammoniumtetrakis(pentafluorophenyl)borate,-   Di(cyclohexyl)ammoniumtetrakis(pentafluorophenyl)borate,-   Triphenylphosphoniumtetrais(phenyl)borate,-   Triethylphosphoniumtetrakis(phenyl)borate,-   Diphenylphosphoniumtetrakis(phenyl)borate,-   Tri(methylphenyl)phosphoniumtetrakis(phenyl)borate,-   Tri(dimethylphenyl)phosphoniumtetrakis(phenyl)borate,-   Triphenylcarbeniumtetrakis(pentafluorophenyl)borate,-   Triphenylcarbeniumtetrais(pentafluorophenyl)aluminate,-   Triphenylcarbeniumtetr-akis(phenyl)aluminate,-   Ferroceniumtetrakis(pentafluorophenyl)borate,-   Ferroceniumtetrakis(pentafluorophenyl)aluminate.-   Triphenylcarbeniumtetrais(pentafluorophenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate.

Organic aluminum compounds used as compound C) are those of formulaH_(j)AlU_(3-j) or H_(j)Al₂U_(6-j) described above. The catalysts of thepresent invention can also be supported on an inert carrier. This isachieved by depositing the metallocene compound A) or the product of thereaction thereof with the component B), or the component B) and then themetallocene compound A) on an inert support such as, for example,silica, alumina, Al—Si, Al—Mg mixed oxides, magnesium halides,styrene/divinylbenzene copolymers, polyethylene or polypropylene. Thesupportation process is carried out in an inert solvent such ashydrocarbon for example toluene, hexane, pentane or propane and at atemperature ranging from 0° C. to 100° C., preferably the process iscarried out at a temperature ranging from 25° C. to 90° C. or theprocess is carried out at room temperature.

A suitable class of supports which can be used is that constituted byporous organic supports functionalized with groups having activehydrogen atoms. Particularly suitable are those in which the organicsupport is a partially crosslinked styrene polymer. Supports of thistype are described in European application EP-633272. Another class ofinert supports particularly suitable for use according to the inventionis that of polyolefin porous prepolymers, particularly polyethylene. Afurther suitable class of inert supports for use according to theinvention is that of porous magnesium halides such as those described inInternational application WO 95/32995.

With the process of the present invention it is possible to obtain1-butene polymers having high molecular weight, measured in terms oftheir intrinsic viscosity (I.V.) and in high yields. Thus, according toanother aspect, the present invention provides 1-butene homopolymershaving the following characteristics:

-   -   isotactic pentads (mmmm)>90, preferably >95;    -   intrinsic viscosity (I.V.) measured in tetrahydronaphtalene        (THN) at 135° C.>1.2, preferably ≧1.5, more preferably >1.9;        even more preferably >2.4;    -   melting point (D.S.C.) higher than 100° C.; and    -   molecular weight distribution Mw/Mn<4, preferably <3.5.

The 1-butene homopolymers of the present invention do not have 4,1insertions (regioerrors) detectable with a 400 MHz spectrometeroperating at 100.61 MHz.

When 1-butene is copolymerized with ethylene, propylene or alpha olefinsof formula CH₂═CHT wherein T is a C₃-C₁₀ alkyl group, a copolymer havinga content of comonomer derived units of up to 50% by mol can beobtained, preferably up to 20% by mol, more preferably from 0.2% by molto 15% by mol. Examples of alpha-olefins of formula CH₂═CHT are1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene,4,6-dimethyl-1-heptene, 1-decene, 1-dodecene. Preferred comonomers to beused in the process according to the present invention are ethylene,propylene and 1-hexene.

In particular, the 1-butene ethylene copolymers obtainable by theprocess of the present invention are endowed with a very low meltingpoint with respect to the ethylene content thus it is possible to lowerthe melting point of the 1-butene/ethylene polymer by adding smallamount of ethylene. furthermore ethylene is used as comonomer in theprocess of the present invention the resulting copolymer shows a highermolecular weight with respect to the homopolymers and the yield of theprocess is improved. Therefore a further embodiment of the presentinvention is a process for preparing copolymer of 1-butene and ethylene,comprising the step of copolymerizing 1-butene and ethylene in thepresence of the catalyst system reported above. Preferably the amount ofethylene in the liquid phase ranges from 0.01 to 30% by weight;preferably from 1% to 10% by weight.

Preferably the 1-butene/ethylene copolymers have an ethylene contentcomprised between 0.2% by mol and 15% by mol; preferably comprisedbetween 1% by mol and 10% by mol; more preferably comprised between 2%by mol and 8% by mol.

Therefore a further object of the present invention is a1-butene/ethylene copolymer having an ethylene content comprised between0.2% by mol and 15% by mol; preferably comprised between 1% by mol and10% by mol; more preferably comprised between 2% by mol and 8% by mol.,obtainable by the process of the present invention, having the followingcharacteristics:

-   -   isotactic pentads (mmmm)>90, preferably >95;    -   intrinsic viscosity (I.V.) measured in tetrahydronaphtalene        (THN) at 135° C.>1.2, preferably ≧1.5, more preferably >1.9;        even more preferably >2.4;        wherein the percent by mol of the ethylene content in the        polymer (C₂) and the melting point of the polymer (Tm) meet the        following relation:

Tm<−4.4C ₂+92.0.

Preferably the relation is Tm<4.4C₂+90.2; more preferably it isTm<4.4C₂+89.2.

The polymerization process of the present invention can be carried outin liquid phase, optionally in the presence of an inert hydrocarbonsolvent, or in gas phase. Said hydrocarbon solvent can be eitheraromatic (such as toluene) or aliphatic (such as propane, hexane,heptane, isobutane, cyclohexane and 2,2,4-trimethylpentane). Preferably,the polymerization process of the present invention is carried out byusing liquid 1-butene as polymerization medium. The polymerizationtemperature preferably ranges from 0° C. to 250° C.; preferablycomprised between 20° C. and 150° C. and, more particularly between 50°C. and 90° C.; The molecular weight distribution can be varied by usingmixtures of different metallocene compounds or by carrying out thepolymerization in several stages which differ as to the polymerizationtemperature and/or the concentrations of the molecular weight regulatorsand/or the monomers concentration. Moreover by carrying out thepolymerization process by using a combination of two differentmetallocene compounds of formula (I) a polymer endowed with a broadmelting is produced. The polymerization yield depends on the purity ofthe transition metal organometallic catalyst compound (A) in thecatalyst, therefore, said compound can be used as such or can besubjected to purification treatments before use.

The polymerization process of the present invention can be carried outin the presence of hydrogen in order to increase the yield. Preferablythe concentration of hydrogen in the liquid phase ranges from 0.5 ppm to20 ppm; more preferably from 1 ppm to 6 ppm. The effect of improving theyield of the process is additive with the effect of ethylene explainedabove.

A further object of the present invention is a metallocene compound offormula (II):

wherein:M is an atom of a transition metal selected from those belonging togroup 3, 4, or to the lanthanide or actinide groups in the PeriodicTable of the Elements; preferably M is zirconium titanium or hafnium; X,equal to or different from each other, is a hydrogen atom, a halogenatom, a R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ group wherein R is alinear or branched, saturated or unsaturated C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkylradical, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; and R′ is a C₁-C₂₀-alkylidene,C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylideneradical; preferably X is a hydrogen atom, a halogen atom, a OR′O or Rgroup; more preferably X is chlorine or a methyl radical; R¹, R², R⁵,R⁷, R⁸ and R⁹, equal to or different from each other, are hydrogenatoms, or linear or branched, saturated or unsaturated C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkylradicals, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; or R⁸ and R⁹ can optionally form asaturated or unsaturated, 5 or 6 membered ring; preferably R¹, R², arethe same and are C₁-C₁₀ alkyl radicals optionally containing one or moresilicon atoms; more preferably R¹ and R² are methyl radicals;R⁸ and R⁹, equal to or different from each other, are preferably C₁-C₁₀alkyl or C₆-C₂₀ aryl radicals; more preferably they are methyl radicals;R⁵ is preferably a hydrogen atom or a methyl radical;R⁷ is preferably a hydrogen atom;R³ and R⁴, equal to or different from each other, are linear orbranched, saturated or unsaturated C₁-C₂₀-alkyl radicals, optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably R³ and R⁴ equal to or different from eachother are C₁-C₁₀-alkyl radicals; more preferably R³ is a methyl, orethyl radical; and R⁴ is a methyl, ethyl or isopropyl radical;R⁶ is a linear or branched, saturated or unsaturated C₁-C₂₀-alkylradical, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; or it can optionally form with R⁵ asaturated or unsaturated, 5 or 6 membered ring, said ring can bearC₁-C₂₀ alkyl radicals as substituents; preferably R⁶ is a C₁-C₁₀alkylradical; more preferably R⁶ is a methyl, ethyl or isopropyl radical;

By using this class of compounds in the process according to the presentinvention polybutene homo or copolymers endowed with a higher molecularweight measured in terms of their intrinsic viscosity (I.V.) and in highyields are obtained.

A further object of the present invention is a ligand of formula (III):

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ have the meaning describedabove.

Metallocene compounds of formula (II) can be obtained by reacting theligand of formula (III) with a compound capable of forming acorresponding dianionic compound thereof and thereafter with a compoundof formula Mx₄, wherein M and X have the meaning described above.Example of compound able to form the dianionic compound are alkyllithium such as methyl lithium or butyl lithium, Grignard reagents ormetallic sodium and potassium.

The following examples are for illustrative purpose and do not intend tolimit the scope of the invention.

EXAMPLES Experimental Section

The intrinsic viscosity (I.V.) was measured in tetrahydronaphtalene(THN) at 135° C.

The melting points of the polymers (T_(m)) were measured by DifferentialScanning Calorimetry (D.S.C.) on a Perkin Elmer DSC-7 instrument,according to the standard method. A weighted sample (5-7 mg) obtainedfrom the polymerization was sealed into aluminum pans and heated to 180°C. at 10° C./minute. The sample was kept at 180° C. for 5 minutes toallow a complete melting of all the crystallites, then cooled to 20° C.at 10° C./minute. After standing 2 minutes at 20° C., the sample washeated for the second time to 180° C. at 10° C./min. In this secondheating run, the peak temperature was taken as the melting temperature(T_(m)) and the area of the peak as melting enthalpy (ΔH_(f)).

Molecular weight parameters and molecular weight distribution for allthe samples were measured using a Waters 150C ALC/GPC instrument(Waters, Milford, Mass., USA) equipped with four mixed-gel columns PLgel20 μm Mixed-A LS (Polymer Laboratories, Church Stretton, UnitedKingdom). The dimensions of the columns were 300×7.8 mm. The solventused was TCB and the flow rate was kept at 1.0 mL/min. Solutionconcentrations were 0.1 g/dL in 1,2,4 trichlorobenzene (TCB). 0.1 g/L of2,6-di-t-butyl-4-methyl phenol (BHT) was added to prevent degradationand the injection volume was 300 μL. All the measurements were carriedout at 135° C. GPC calibration is complex, as no well-characterizednarrow molecular weight distribution standard reference materials areavailable for 1-butene polymers. Thus, a universal calibration curve wasobtained using 12 polystyrene standard samples with molecular weightsranging from 580 to 13,200,000. It was assumed that the K values of theMark-Houwink relationship were: K_(PS)=1.21×10⁻⁴, dLg andK_(PB)=1.78×10⁻⁴ dL/g for polystyrene and poly-1-butene respectively.The Mark-Houwink exponents a were assumed to be 0.706 for polystyreneand 0.725 for poly-1-butene. Even though, in this approach, themolecular parameters obtained were only an estimate of the hydrodynamicvolume of each chain, they allowed a relative comparison to be made.

¹³C-NMR spectra were acquired on a DPX-400 spectrometer operating at100.61 MHz in the Fourier transform mode at 120° C. The samples weredissolved in 1,1,2,2-tetrachloroethane-d2 at 120° C. with a 8% wt/vconcentration. Each spectrum was acquired with a 90° pulse, 15 secondsof delay between pulses and CPD (waltz16) to remove ¹H-¹³C coupling.About 3000 transients were stored in 32K data points using a spectralwindow of 6000 Hz. The isotacticity of metallocene-made PB is measuredby ¹³C NMR, and is defined as the relative intensity of the mmmm pentadpeak of the diagnostic methylene of the ethyl branch. This peak at 27.73ppm was used as internal reference. Pentad assignments are givenaccording to Macromolecules, 1992, 25, 6814-6817. After baselinecorrection, this region is integrated between 28.60-27.27 ppm(mmmm+mmmr+mmrr) and 26.78-26.48 ppm (mrrm). The phase of the twointegrals is then corrected and the first integral splitted at 27.4 ppmto separate the mmrr pentad contribution. The mmmr peak overlaps withthe base of the mmmm pentad and cannot be separated. Statisticalmodelling of pentad distributions was done using a model based on.enantiomorphic site control as a function of the probability parameter b(for the insertion of the preferred enantioface), as described in Chem.Rev. 2000, 100, 1253-1345.

Taking into account the overlap between the mmmm and the mmmr pentads,the following expression were used:

mmmm+mmmr=b ⁵+(1−b)⁵+2[b ⁴(1−b)+b(1−b)⁴]

mmrr=2[b ⁴(1−b)+b(1−b)⁴]

mrrm=b ⁴(1−b)+b(1−b)⁴

Assignments of 4,1 insertion were made according to V. Busico, R.Cipullo, A. Borriello, Macromol. Rapid. Commun. 1995, 16, 269-274.

Preparation of Catalyst Components

Racdimethylsilyl{(2,4,7-trimethyl-1-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)}zirconiumdichloride (A-1);dimethylsilyl{(1-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)}zirconiumdichloride (A-2);dimethylsilyl{(2-methyl-1-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)}zirconiumdichloride (A-3) were prepared according to WO 01/47939.

Synthesis ofdimethylsilyl[1-(2,4,6-trimethyl-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophenyl)]zirconiumdichloride (A-4) a) Synthesis ofchloro(2,4,6-trimethyl-indenyl)dimethylsilane

A 2.5 M n-BuLi solution in hexane (37.2 mL, 0.093 mol) was addeddropwise at 0° C. under nitrogen atmosphere to a solution of 14.00 g of2,4,6-trimethyl-indene (prepared according to Eur. Pat. Appl. 693,506)in 100 mL of Et₂O in a 500 mL 3-necked round flask. During the additiona white suspension was formed. The mixture was then allowed to warm upto r.t. and stirred for 30 min, with final formation of a whitesuspension. Then a solution of Me₂SiCl₂ (98%, d=1,064, 11.28 mL, 0.093mol.) in 30 mL of THF was cooled to 0° C. and slowly added to thelithium salt suspension, also cooled to 0° C. The reaction mixture wasallowed to warm up to r. t. and stirred for 2 h with final formation ofa light yellow suspension. The solvents were then removed in vacuo andthe residue was extracted with 150 mL of toluene to remove the LiCl. Thelight yellow filtrate was brought to dryness in vacuo to give 21.53 g ofa yellow oil, characterized by ¹NMR analysis as the target product,yield 97.5%. This product was used as such in the next step withoutfurther purification.

b) Synthesis of1-(2,4,6-trimethyl-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]dithiophene)dimethylsilane

A 2.5 M n-BuLi solution in hexane (16.74 mL, 41.85 mmol) was addeddropwise at 0° C. under stirring to a solution of 8.21 g of2,5-dimethyl-7H-cyclopenta[1,2-b:4,3-b′]-dithiophene (39.79 mmol) in 150mL of Et₂O in a 500 mL 3-necked round flask. At the end of the addition,the resulting dark suspension was stirred for 30 min at r. t. A solutionof chloro(2,4,6-trimethyl-indenyl)dimethylsilane (10.00 g, 39.87 mmol)in 20 mL of THF was cooled to 0° C. and slowly added to the abovesuspension, with final formation of a dark suspension. The latter wasallowed to warm up to room temperature and stirred for 3 h. Then thereaction mixture was concentrated under reduced pressure to give a darksolid, which was extracted at r. t. with 150 mL of toluene to remove theLiCl. The extract was dried in vacuo to give 17.37 g of a dark coloredsticky foam. The ¹NMR analysis showed the presence of the desired ligandtogether with some impurities. The product was used as such in the nextstep without further purification.

c) Synthesis ofdimethylsilyl[1-(2,4,6-trimethyl-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophenyl)]zirconiumdichloride (A-4)

A 2.5 M n-BuLi solution in hexane (33.86 mL, 84.65 mmol) was addeddropwise at 0° C. under stirring to a solution of 17.37 g of1-(2,4,6-trimethyl-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)dimethylsilane(41.29 mmol) in 200 mL of Et₂O in a 500 mL 3-necked round flask. Theresulting dark suspension was allowed to warm up to r.t and stirred for1 h. Then a suspension of 9.55 g of ZrCl₄ (40.98 mmol) in 100 mL oftoluene was prepared, cooled to 0° C. and slowly added to the lithiumsalt mixture, previously cooled to 0° C. too. The resulting reactionmixture was stirred at r. t. for 12 h. The solvents were removed invacuo yielding a residue, which was treated at r. t. with toluene (2×150mL) and filtered on a G4 frit. The residue was further washed withtoluene, while the filtrates were collected and discarded. The residuewas dried in vacuo to give 17.24 g of a brick-red powder, which resultedto be the desired complex by NMR analysis, containing about 20% wt. ofLiCl (yield 57.8%).

Synthesis ofdimethylsilanediyl{1-(2-methyl-4,6-disopropylindenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)}zirconiumdichloride (A-5) a) Synthesis ofchloro(2-methyl-4,6-disopropyl-1-indenyl)dimethylsilane

A 2.3 M HexLi solution in hexane (6.00 mL, 13.80 mmol) was addeddropwise at 0° C. to a solution of 2.93 g of2-methyl-4,6-diisopropyl-1-indene (13.67 mmol) in 30 mL of Et₂O. At theend of the addition, the resulting white suspension was allowed to warmup to room temperature and stirred for 1 h. A solution of Me₂SiCl₂ (99%,1.68 mL, d=1.064, 13.68 mmol) in 10 mL of Et₂O was added at 0° C. to thelithium salt solution, previously cooled to 0° C. The reaction mixturewas allowed to warm up to room temperature and stirred for 3 h withfinal formation of a white suspension. The solvents were removed invacuo and the residue was extracted with 30 mL of toluene to remove theLiCl. The filtrate was brought to dryness in vacuo at 40° C. to give3.33 g of a thick orange oil. Crude yield=79.4%.

¹H NMR (δ, ppm, CDCl₃): 0.12 (s, 3H, Si—CH₃); 0.45 (s, 3H, Si—CH₃);1.28-1.36 (m, 12H, CH₃); 2.31 (m, 3H, CH₃); 2.97 (m, 1H, J=7.43 Hz, CH);3.24 (m, 1H, J=7.43 Hz, CH); 3.58 (s, 1H, CH); 6.77 (m, 1H, Cp-H); 7.01(bm, 1H, Ar); 7.20 (bm, 1H, Ar).

b) Synthesis of1-(2-methyl-4,6-disopropylindenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)dimethylsilane

A 2.3 M HexLi solution in hexane (3.00 mL, 6.90 mmol) was added dropwiseat 0° C. to a suspension of 1.41 g of2,5-dimethyl-7H-cyclopenta[1,2-b:4,3-b′]-dithiophene (6.83 mmol) in 30mL of Et₂O. The resulting brown solution was stirred at 0° C. for 1 hand then a solution of 2.10 g ofchloro(2-methyl-4,6-disopropyl-1-indenyl)dimethylsilane (6.84 mmol) in20 mL of Et₂O was added at the same temperature. The reaction mixturewas then allowed to warm up to room temperature and stirred for 3 h withfinal formation of a brown suspension. The solvents were evaporatedunder reduced pressure and the residue was extracted with 30 mL oftoluene. The extract was dried in vacuo to give 2.79 g of a stickydark-brown solid, which was analyzed by ¹H-NMR spectroscopy. The lattershowed the presence of the expected ligand, crude yield=68.5%. Theproduct was used as such in the next step without further purification.

¹H NMR (δ, ppm, CD₂Cl₂): −0.34 (s, 3H, Si—CH₃); -0.32 (s, 3H, Si—CH₃);1.27-1.39 (m, 12H, CH₃); 2.60 (s, 3H, CH₃); 2.62 (s, 3H, CH₃); 2.67 (s,3H, CH₃); 2.96 (m, 1H, J=7.24 Hz, CH); 3.29 (m, 1H, J=7.24 Hz, CH); 3.87(s, 1H, CH); 4.04 (s, 1H, CH); 6.82 (bs, 1H, Cp-H); 6.92 (m, 1H, CH);6.94 (m, 1H, CH); 7.03 (bs, 1H, Ar); 7.23 (bs, 1H, Ar).

c) Synthesis ofdimethylsilanediyl{1-(2-methyl-4,6-disopropylindenyl)-7-(2,5dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)}zirconium dichloride(A-5)

A 2.3 M HexLi solution (5.1 mL, 11.73 mmol) was added dropwise at 0° C.to a solution of 2.79 g of1-(2-methyl-4,6-disopropylindenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)dimethylsilane (5.85 mmol) in 30 mL of Et₂O. At the end of the addition,the resulting brown solution was stirred for 1 h at room temperature.Then it was cooled again to 0° C. to add a suspension of 1.36 g of ZrCl₄(5.83 mmol) in 15 mL of toluene, previously cooled to 0° C. The reactionmixture was then allowed to warm up to room temperature and stirred for16 h with final formation of a light brown suspension. The solvents wereremoved in vacuo and the crude residue was treated with 25 mL oftoluene. The obtained suspension was filtered: the filtrate waseliminated, while the residue was dried to give 2.25 g of an orangepowder, which resulted to be the target complex, yield=60.6% with LiCl.0.9 g of this powder were treated with a mixture of 10 mL of toluene and2 mL of isobutanol and stirred for 15 min at room temperature. Themixture was then filtered: the filtrate containing LiCl and by-productsdue to decomposition was discarded, while the residue was concentratedin vacuo yielding 0.5 g of an orange powder free from LiCl. This powderresulted to be the pure complex by ¹H NMR analysis.

¹H NMR (δ, ppm, CD₂Cl₂): 1.18 (s, 3H, Si—CH₃); 1.34 (s, 3H, Si—CH₃);1.19 (d, 3H, J=6.85 Hz, CH₃); 1.20 (d, 3H, J=6.85 Hz, CH₃); 1.26 (d, 3H,J=6.85 Hz, CH₃); 1.35 (d, 3H, J=6.85 Hz, CH₃); 2.39 (s, 3H, CH₃); 2.42(d, 3H, J=1.17 Hz, CH₃); 2.61 (d, 3H, J=1.17 Hz, CH₃); 2.82 (m, 1H,J=6.85 Hz, CH); 3.06 (m, 1H, J=6.85 Hz, CH); 6.64 (q, 1H, J=1.17 Hz,CH); 6.78 (q, 1H, J=1.17 Hz, CH); 6.80 (s, 1H, Cp-H); 6.93 (bt, 1H, Ar,H5); 7.32 (bq, 1H, Ar, H7).

Synthesis of racdimethylsilyl{(2,4,7-trimethyl-1-indenyl)-7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)}zirconiumdimethyl (A-6)

The ligand,[3-(2,4,7-trimethylindenyl)][7-(2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene)]dimethylsilane, was prepared as described in WO 01/47939. 30.40 g of this ligand(72.26 mmol) and 170 ml of anhydrous THF were charged under nitrogen ina cylindrical glass reactor equipped with magnetic stirring bar. Thebrown solution so obtained was cooled and maintained at 0° C., while58.4 ml of n-BuLi 2.5M in hexane (146 mmol) were added dropwise viadropping funnel. At the end of the addition, the dark brown solution wasstirred for 1 hour at room temperature, then cooled to −50° C., and then48.6 ml of MeLi 3.05 M in diethoxymethane (148.2 mmol) were added to it.In a Schlenk, 16.84 g of ZrCl₁₋₄ (72.26 mmol) were slurried in 170 ml oftoluene. Both mixtures were kept at −50° C. and the ZrCl₄ slurry wasquickly added to the ligand dianion solution. At the end of theaddition, the reaction mixture was allowed to reach room temperature andstirred for an additional hour. A yellow-green suspension was obtained.¹H NMR analysis shows complete conversion to the target complex. Allvolatiles were removed under reduced pressure, and the obtained freeflowing brown powder was suspended in 100 ml of Et₂O. After stirring fora few minutes, the suspension was filtered over a G4 frit. The solid onthe frit was then washed twice with Et₂O (until the washing solventturns from brown to yellow), then dried under vacuum, and finallyextracted on the frit with warm toluene (60° C.), until the filteringsolution turns from yellow to colorless (about 650 ml of toluene); Theextract was dried under reduced pressure to give 28.6 g of yellowpowder, which ¹H-NMR showed to be the target complex, free fromimpurities. The yield based on the ligand was 73.3%.

¹H-NMR: (CD₂Cl₂, r.t.), ppm: −2.09 (s, 3H), −0.79 (s, 3H), 1.01 (s, 3H),1.04 (s, 3H), 2.38 (s, 3H), 2.39 (s, 3H), 2.43 (d, 3H, J=1.37 Hz), 2.52(s, 3H), 2.57 (d, 3H, J=1.37 Hz), 6.61 (dq, 1 H, 3=7.04 Hz, J=0.78 Hz),6.81 (q, 1H, J=1.37 Hz), 6.85 (dq, 1H, J=7.04 Hz, J=0.78 Hz), 6.87 (q,1H, J=1.37 Hz), 6.91 (s, 1H).

Polymerization Examples 1-5 and Comparative Examples 6-7

The cocatalyst methylalumoxane (MAO) was a commercial product which wasused as received (Witco AG, 10% wt/vol toluene solution, 1.7 M in Al).The catalyst mixture was prepared by dissolving the desired amount ofthe metallocene with the proper amount of the MAO solution, (Al/Zrratio=500) obtaining a solution which was stirred for 10 min at roomtemperature before being injected into the autoclave.

Polymerization (General Procedure)

6 mmol of Al(i-Bu)₃ (as a 1M solution in hexane) and 1350 g of 1-butenewere charged at room temperature in a 4-L jacketed stainless-steelautoclave, equipped with magnetically driven stirrer and a 35-mLstainless-steel vial, connected to a thermostat for temperature control,previously purified by washing with an Al(i-Bu)₃ solution in hexanes anddried at 50° C. in a stream of nitrogen. The autoclave was thenthermostated at the polymerization temperature, and then the toluenesolution containing the catalyst/cocatalyst mixture was injected in theautoclave by means of nitrogen pressure through the stainless-steelvial, and the polymerization carried out at constant temperature for thetime indicated in Table 1. Then stirring is interrupted; the pressureinto the autoclave is raised to 20 bar-g with nitrogen. The bottomdischarge valve is opened and the 1-butene/poly-1-butene mixture isdischarged into a heated steel tank containing water at 70° C. The tankheating is switched off and a flow of nitrogen at 0.5 bar-g is fed.After cooling at room temperature, the steel tank is opened and the wetpolymer collected. The wet polymer is dried in an oven under reducedpressure at 70° C. The polymerization conditions and thecharacterization data of the obtained polymers are reported in Table 1.

TABLE 1 time Yield kg/ I.V. mmmm 4,1 T_(m) EX Met mg T_(pol) (min) (g)(g_(cat)*h) (dL/g) M_(w)/M_(n) % regioerrors (Form II) 1 A-1 2 60 60 13065.0 2.4 3.1 95.8 n.d. 105.5 2 A-1 2 70 60 125 62.5 2.0 3.9 95.3 n.d.104.4 3 A-1 2 80 60 100 50.0 1.3 3.7 95.2 n.d. 103.9 4 A-4 3 70 60 82.527.5 1.7 n.a. n.a. n.a. 101 5 A-5 2 70 60 86.6 43.3 1.5 n.a. n.a. n.a.100.2 3* A-2 4 60 15 80 80.0 0.5 n.a. 85.5 n.d. 78 4* A-3 3 70 60 10936.3 1.3 3.1 89.0 n.d. 84 *= comparative n.d. = not detectable n.a. =not available

Examples 6-8 Influence of Hydrogen

The procedure of examples 1-5 has been repeated with the metallocenecompound A-1 and an Al(MAO)/Zr ratio of 200, with the exception that anamount of H₂ reported in table 3 is injected into the autoclave beforethe injection of the catalyst solution. The results are reported intable 3

TABLE 3 I.V. T_(pol) time H₂ H₂ kg_(PB)/ dL/g, M_(v) Ex mg ° C. (min)NmL ppm ⁺ (g_(mtcene) × h) (THN) (IV_(THN)) 6 2 70 60 0 0 82.5 2.34 479800 7 2 70 60 100 2 163 n.a. n.a. 8 2 70 60 200 4 220 1.44 245 600 n.a.not available ⁺ ppm in liquid phaseFrom these examples result that hydrogen can be used as activating agentin order to increase the final yield.

Examples 9-12 ethylene/1-butene copolymers

The cocatalyst methylalumoxane (MAO) was a commercial product which wasused as received (Crompton 10% wt/vol 1.7 M in Al). The catalyst mixturewas prepared by dissolving 2 mg of A-1 with the proper amount of the MAOsolution, (Al/Zr ratio=200) obtaining a solution which was stirred for10 min at room temperature before being injected into the autoclave.

A 4.25 litres steel autoclave, equipped with magnetically stirred anchor(usual stirring rate 550 rpm) and with different Flow Record & Controlsystems (FRC), among which a FRC having maximum flow rate of 9000gr/hour for 1-butene and two FRC having maximum flow rate of 500 and 30g/h for ethylene is cleaned with warm nitrogen (1.5 barg N₂, 70° C., 1hour). After the above mentioned autoclave cleaning, the stirringstarts, 1-butene is fed into the reactor (1350 gr at 30° C.) with theamount of ethylene reported in table 4, together with 6 mmol ofAl(i-Bu)₃ (TIBA) (as a 1 M solution in hexane). Subsequently, thereactor inner temperature is raised from 30° C. to 70° C., thepolymerisation temperature; as a consequence the pressure increases.When pressure and temperature are constant, the catalytic solution isfed into the reactor with a nitrogen overpressure and the polymerisationpressure is kept constant feeding only ethylene (amount indicated intable 3). The polymerisation is run for 60 minutes. Then the stirring isinterrupted; the pressure into the autoclave is raised to 20 bar-g withnitrogen. The bottom discharge valve is opened and the1-butene/poly-1-butene mixture is discharged into the steel heated tankcontaining water at 70° C. The tank heating is switched off and a fluxof 0.5 bar-g nitrogen is fed. After 1 hour cooling at room temperaturethe steel tank is opened and the wet polymer collected. The wet polymeris dried in a oven under nitrogen at 70° C. The polymerizationconditions and the characterization data of the obtained polymers arereported in Table 4

TABLE 4 C₂ in liq. activity C₂ in copol. R I.V. phase C₂ fed kg_(PB)/mol % (C₂/C₄)_(copo)/ dL/g T_(m) mmmm ΔH Ex % wt g (g_(mtcene) × h)(NMR) (C₂/C₄)_(liq. phase) THN (Form II) % J/g  9 0.19 2.6 58 2.28 6.12.61 77.8 >90 19.4 10 0.38 4.1 88 2.99 4.0 2.65 75.7 >90 15.7 11 0.647.4 122 6.24 5.2 2.56 60.9 >90 0.8 12 0.38 9 191 n.a. n.a. n.a. n.a.n.a. n.a. n.a. not allowableFrom table 4 it results that the yield of the process of the presentinvention can be increased by using ethylene or both ethylene andhydrogen (example 16). In addition the use of ethylene further increasesthe molecular weight of the polymer.

1. A process for preparing 1-butene polymers, said process comprising polymerizing 1-butene or copolymerizing 1-butene with ethylene, propylene or an alpha-olefin of formula CH₂═CHT wherein T is a C₃-C₁₀ alkyl group, in the presence of a catalyst system obtainable by contacting: (A) a metallocene compound having the following formula (I)

wherein: M is an atom of a transition metal selected from those belonging to group 3, 4, or to the lanthanide or actinide groups in the Periodic Table of the Elements; X, equal to or different from each other, is a hydrogen atom, a halogen atoms or R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ group, wherein R is a linear or branched, saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and the R′ is a C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylidene radical. R¹, R², R⁵, R⁶, R⁷, R⁸ and R⁹, equal to or different from each other, are hydrogen atoms, or linear or branched, saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or R⁵ and R⁶, and/or R⁸ and R⁹ can optionally form a saturated or unsaturated, 5 or 6 membered rings, said ring can bear C₁-C₂₀ alkyl radicals as substituents; with the proviso that at least one of R⁶ or R⁷ is a linear or branched, saturated or unsaturated C₁-C₂₀-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R³ and R⁴, equal to or different from each other, are linear or branched, saturated or unsaturated C₁-C₂₀-alkyl, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and (B) an alumoxane and/or a compound capable of forming an alkyl metallocene cation.
 2. The process according to claim 1 wherein in the metallocene of formula (I) R⁷ is preferably a linear or branched, saturated or unsaturated C₁-C₂₀-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; otherwise when R⁶ is different from a hydrogen atom, R⁷ is a hydrogen atom.
 3. The process according to claims 1 or 2 wherein the catalyst system is obtained by further contacting the components (A) and (13) with: (C) an organo aluminum compound.
 4. The process according to anyone of claims 1-3 wherein in the metallocene of formula (I) X is a hydrogen atom, a halogen atom or a OR′O or R group wherein R is a linear or branched, saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl, or C₇-C₂₀-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements and R′ is a divalent radical selected from the group consisting of C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, and C₇-C₂₀-arylalkylidene radicals.
 5. The process according to anyone of claims 1 to 4 wherein in the metallocene of formula (I) R¹ and R² are the same and are C₁-C₁₀ allyl radicals optionally containing one or more silicon atoms.
 6. The process according to anyone of claims 1 to 5 wherein in the metallocene of formula (I) R⁸ and R⁹, equal to or different from each other, are C₁-C₁₀ alkyl or C₆-C₂₀ aryl radicals; R⁵ is hydrogen atoms or methyl radicals and R⁶ is a hydrogen atom or a methyl, ethyl or isopropyl radical.
 7. The process according to anyone of claims 1 to 6 wherein in the metallocene of formula (I) R³, R⁴ and R⁷, equal to or different from each other, are C₁-C₁₀ alkyl radicals.
 8. The process according to anyone of claims 1 to 7 wherein the compound of formula (I) has formula (Ia) or (Ib):

Wherein M, X, R¹, R², R⁸ and R⁹ have the meaning described in claim 1; R³ and R⁴, equal to or different from each other, are linear or branched, saturated or unsaturated C₁-C₂₀-alkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R⁶ and R⁷ are a linear or branched, saturated or unsaturated C₁-C₂₀-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements.
 9. The process according to claim 8 wherein R³, R⁴, R⁶ and R⁷ are C₁-C₁₀-alkyl radicals.
 10. The process according to anyone of claims 1-9 wherein 1-butene and ethylene are copolymerized in the presence of the catalyst system reported above.
 11. The process according to claim 10 wherein the amount of ethylene in the liquid phase ranges from 0.01 to 30% by weight.
 12. The process according to anyone of claims 1-12 wherein said process is carried out in the presence of hydrogen.
 13. The process according to claim 12 wherein the concentration of hydrogen in the liquid phase ranges from 0.5 ppm to 20 ppm.
 14. A 1-butene homopolymer having the following characteristics: isotactic pentads (mmmm)>90; intrinsic viscosity (I.V.) measured in tetrahydronaphtalene (THN) at 135° C.>1.2; melting point (D.S.C.) higher than 100° C.; and molecular weight distribution Mw/Mn<4;
 15. A 1-butene homopolymer having the following characteristics: isotactic pentads (mmmm)>95; intrinsic viscosity (I.V.) measured in tetrahydronaphtalene (THN) at 135° C.>1.5; melting point (D.S.C.) higher than 100° C.; and molecular weight distribution Mw/Mn<4.
 16. A 1-butene/ethylene copolymer having an ethylene content comprised between 0.2% by mol and 15% by mol obtainable by the process of claim 1 having the following characteristics: isotactic pentads (mmmm)>90 intrinsic viscosity (I.V.) measured in tetrahydronaphtalene (THN) at 135° C.>1.2 wherein ethylene content in the polymer (C₂) (% by mol) and the melting point of the polymer (Tm) meet the following relation: Tm<−4.4C ₂+92.0.
 17. A metallocene compound of formula (II):

wherein: M is an atom of a transition metal selected from those belonging to group 3, 4, or to the lanthanide or actinide groups in the Periodic Table of the Elements; X, equal to or different from each other, is a hydrogen atom, a halogen atom, a R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ group wherein R is a linear or branched, saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R′ is a C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylidene radical; R¹, R², R⁵, R⁶, R⁷, R⁸ and R⁹, equal to or different from each other, are hydrogen atoms, or linear or branched, saturated or unsaturated C₁-C₂₀-alkyl C₃-C₂₀-cycloalkyl C₆-C₂₀-aryl C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or R⁸ and R⁹ can optionally form a saturated or unsaturated, 5 or 6 membered ring; R³ and R⁴, equal to or different from each other, are linear or branched, saturated or unsaturated C₁-C₂₀-alkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; R⁶ is a linear or branched, saturated or unsaturated C₁-C₂₀-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or it can optionally form with R⁵ a saturated or unsaturated, 5 or 6 membered ring, said ring can bear C₁-C₂₀ alkyl radicals as substituents.
 18. The metallocene compound according to claim 17 wherein: R¹, R², are the same and are C₁-C₁₀ alkyl radicals optionally containing one or more silicon atoms; R⁸ and R⁹, equal to or different from each other, are C₁-C₁₀ alkyl or C₆-C₂₀ aryl radicals; R⁵ is a hydrogen atom or a methyl radical; R⁷ is a hydrogen atom; R³ and R⁴ equal to or different from each other are C₁-C₁₀-alkyl radicals; R⁶ is a C₁-C₁₀-alkyl radical.
 19. A ligand of formula (III):

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ have the meaning described in claim
 12. 